Cumulative biosensor system to detect alcohol

ABSTRACT

A wearable device may be provided for detecting cumulative alcohol consumption. Such a wearable device may include an adhesive layer that adheres to skin and that allows sweat from the skin to pass through and a customizable ink layer that reacts irreversibly to change color along a gradient as ethanol is detected in the sweat. The customizable ink continues to increase color intensity along the gradient as ethanol continues to be detected in the sweat over time.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a continuation of International patentapplication number PCT/US18/16281 filed Jan. 31, 2018, which claims thepriority benefit of U.S. provisional patent application No. 62/452,579filed Jan. 31, 2017, the disclosures of which are incorporated byreference herein.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to biosensors. Morespecifically, the present invention relates to cumulative biosensorsystems for detecting alcohol.

2. Description of the Related Art

The usage of alcohol has many negative health and economic effects onindividuals as well as society. In the United States (US) alone,excessive alcohol use led to approximately 90,000 deaths in the lastyear and is responsible for 10% of deaths in working-age adults, makingalcohol-related deaths the fourth leading preventable cause of death(4). In addition, the economic burden of excessive alcohol consumptionis enormous. In 2006, this cost was estimated at $223.5 billion in theUS, or approximately $700 per individual (5).

The current market for alcohol monitoring technologies is primarilycatered to alcohol enforcement at the government and business level. Andwhile there are consumer grade options on the market, these availabledevices have major practical limitations for widespread use. They arebulky, electronics-dependent, and expensive. Even so called personalbreathalyzers are only small enough to fit on a keychain. Moreover,these devices require active and “correct” use by the customer; i.e.customers must blow into the device in a specific way, for a set amountof time, or they may get an incorrect reading (6). This active use mayalso carry a strong stigma preventing true widespread use. The abilityto conceal or personalize current breathalyzers and transdermal BACdevices does not exist today, as their electronics dictate a certainarrangement and size. Finally, since breathalyzers are not continuouslysensing devices, they cannot offer a continuous cumulative readout ofone's alcohol consumption.

Alcohol may further be linked to certain crimes, including date rapeswhich inflict a profound emotional and physiological impact on victims.Recent studies, conducted by the University of Iowa, (7) which includevictims of attacks at US college campuses, highlight both the emotionaland staggering victimization costs (up to $151,423 in one instance).

There is, therefore, a need in the art for improved systems and methodsfor cumulative biosensor-based detection of alcohol.

SUMMARY OF THE CLAIMED INVENTION

The present invention includes a wearable biosensor that detectscumulative alcohol consumption, as well as an associated computingdevice application. In particular, the wearable biosensor is capable todetecting cumulative consumption of alcohol over time (e.g., since thebiosensor was applied). As such, the biosensor readings differs frompresently known methods of measuring alcohol consumption (e.g.,Breathalyzer), which reflect only a current level of alcohol content.The biosensor described herein, however, reflects a cumulative amount ofalcohol that has been consumed over the course of time since thebiosensor was first applied (e.g., throughout the course of an evening).The detected accumulation of alcohol may be reflected in a variety ofways, including colors (and gradients of the same), as well as othervisual and sensory means.

In one embodiment, an alcohol monitoring solution is offered thataddresses many problems discussed above. Furthermore, such solution mayappeal to a significantly larger market and user demographic, as learnedfrom surveying 250 subjects across age, sex, education, drinking habits,and geography in the US. For example, a statistically significantindicator from these surveys was that women who drink casually are themost likely user segment to wear an electronics-free temporary tattoothat indicates alcohol levels via colorimetry. The form factor may serveas an adequate safety net, for example, during a date.

The ability to monitor alcohol consumption in a cumulative fashion bysimple means has the potential to raise awareness of alcohol usage andcould promote a healthier lifestyle across a wide user demographic,including young adults. For example, in cases where an individual'shabitual drinking is gradually becoming more common, the devicedescribed herein could help identify and prevent a nascent negativetrend developing into a severe health condition. In general, byaddressing alcohol-related problems at their onset and throughout theirdevelopment, the present invention may contribute more effectively tothe mitigation of the health and economic burdens that suchalcohol-related problems eventually devolve into.

Some embodiments may include a wearable instantaneous alcohol biosensor,as well as a related biosensor that detects cumulative alcohol levels.To allow for the option of tracking values electronically over longerperiods of time, computer vision algorithms may be developed and trainedto permanently record and interpret cumulative alcohol levels for theindividual. Electronic tracking may allow for further guidance andawareness, and enabling anonymized data collection for researchpurposes.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an exemplary temporary tattoo that may be part of awearable biosensor system for cumulative detection of alcohol.

FIG. 2A illustrates an exemplary composition for a temporary tattoo thatmay be part of a wearable biosensor system for cumulative detection ofalcohol.

FIG. 2B illustrates an exemplary application of a temporary tattoo thatmay be part of a wearable biosensor system for cumulative detection ofalcohol.

FIG. 2C illustrates an exemplary implementation of a temporary tattoothat may be part of a wearable biosensor system for cumulative detectionof alcohol.

FIG. 2D illustrates an alternative exemplary implementation including anassociated application for use with a temporary tattoo that may be partof a wearable biosensor system for cumulative detection of alcohol.

FIG. 3A is a graph correlating alcohol percentages to color-strength ofan exemplary alcohol-sensing ink formulation.

FIG. 3B is a graph illustrating color change kinetics of an exemplaryalcohol-sensing ink formulation.

FIG. 3C is a graph correlating sweat concentrations with colorabsorbance change of an exemplary alcohol-sensing ink formulation.

FIG. 3D illustrates exemplary sweat samples compared to a controlsolution.

FIG. 4A illustrates exemplary capture of raw image using smartphonecamera.

FIG. 4B illustrates exemplary detection of a temporary tattoo on skin.

FIG. 4C illustrates exemplary identification of the different elementsof the temporary tattoo against a reference.

FIG. 4D illustrates exemplary analysis and interpretation of alcoholconcentration values based on shape and color values at specificenvironmental conditions.

FIG. 4E illustrates exemplary storage of all data collected includingthe temporary tattoo extracted shape but excluding actual photographicimages.

FIG. 5 illustrates a variety of customized designs for wearable alcoholbiosensors.

DETAILED DESCRIPTION

The present invention includes a wearable biosensor that detectscumulative alcohol consumption, as well as an associated computingdevice application. In particular, the wearable biosensor is capable todetecting cumulative consumption of alcohol over time (e.g., since thebiosensor was applied). As such, the biosensor readings differs frompresently known methods of measuring alcohol consumption (e.g.,Breathalyzer), which reflect only a current level of alcohol content.The biosensor described herein, however, reflects a cumulative amount ofalcohol that has been consumed over the course of time since thebiosensor was first applied (e.g., throughout the course of an evening).The detected accumulation of alcohol may be reflected in a variety ofways, including colors (and gradients of the same), as well as othervisual and sensory means.

In addition, an associated computing device application may beoptionally used with the wearable biosensor to track alcohol consumptiontrends over longer periods of time. Such an application may receiveinput regarding the reaction exhibited by the wearable biosensorindicating a cumulative amount of alcohol that has been detected. Suchinput may occur in the form of camera image, user input (e.g., selectingfrom a menu), or a wireless communication (e.g., in embodiments wherethe wearable biosensor may be coupled to a radio transmitter). Suchinput may be evaluated to determine what level of cumulative alcoholconsumption is indicated and stored. The input may further be analyzedin context with previous input associated with the same user to identifytrends, anomalies, and various other health or physical conditions ofinterest. In some embodiments, the application may further be trainedand calibrated for more accurate or more detailed, granular results.

Some embodiments may include a wearable, electronics-free, cumulativealcohol biosensor, and an optional mobile companion app. FIG. 1illustrates an exemplary temporary tattoo that may be part of a wearablebiosensor system for cumulative detection of alcohol. For example, anenzymatic reaction may be calibrated for variable sweat flow ratesresults in a colorimetric output correlated to the amount of ethanolcirculating in the blood since the sensor was applied. Furtherembodiments may include a new computer vision pipeline that includes theuse of recent artificial intelligence (AI) techniques to capture a rawimage, detect the cumulative biosensor under diverse conditions,identify color changes, interpret the color changes with respect to thecumulative alcohol levels, and store this information for the user. Suchfunctionalities make significant progress along a product developmentstrategy that includes the following product differentiators:

Passive, continuous, and cumulative. Effortlessly raises awareness abouta user's overall alcohol consumption patterns and how they may bechanging over time.

Easy to wear, learn, and use. Worn much like a regular temporary tattooor sticker, a wearable biosensor relies on the observation of colorchanges with the unaided eye, without strictly requiring the use of aseparate device or application to understand the sensor; i.e., thetattoo is the user interface. A smartphone application may be offered tousers as an option, not a requirement, thus maintaining a low thresholdfor user adoption while allowing smartphone users to track values overlonger periods of time, and eventually providing other services and upsale opportunities.

Low cost. Whereas currently available solutions areelectronics-dependent, the biosensors described herein are not.

Greater privacy and control of information encourages more people towear an alcohol biosensor. Wearable alcohol biosensors can have asemi-arbitrary or user-specific design, potentially concealinginformation such that only the user understands its meaning. It can alsobe placed on different parts of the body, e.g. in the underarm or on thechest. When noticed, it bypasses the perception of being a medicaldevice, thereby reducing the associated risk of stigmatization.

FIGS. 2A-D illustrates various aspects to temporary tattoos that may bepart of a wearable biosensor system for cumulative detection of alcohol.FIG. 2A illustrates an exemplary composition of a temporary tattoo thatincludes transfer adhesive, active ink, and tattoo paper. A formulatedalcohol active ink may be screen printed onto tattoo paper alongside aspectrum of traditional inks that act as reference colors for the user.

FIG. 2B illustrates an exemplary application of a temporary tattoo thatmay be part of a wearable biosensor system for cumulative detection ofalcohol. The combination of inks may be transferred or applied to theskin of the user in much the same way a temporary tattoo may be applied.For example, after removal of the transfer adhesive film, the temporarytattoo paper (printed with ink and associated with adhesive) is readyfor application to skin. Tattoo paper with ink is firmly pressed to skinfor 20-40 seconds after which water is applied to the back of the tattoopaper, facilitating release of the transfer paper. Transfer paper isremoved from the skin leaving the desired active ink allowing forcumulative alcohol levels to be visualized and compared againstreference colors.

FIG. 2C illustrates an exemplary implementation of a temporary tattoothat may be part of a wearable biosensor system for cumulative detectionof alcohol. Once applied to the skin, sweat from the skin is absorbedinto the active ink layer, where colorimetric changes allow for easyvisualization.

FIG. 2D illustrates an alternative exemplary implementation including anassociated application for use with a temporary tattoo that may be partof a wearable biosensor system for cumulative detection of alcohol. Amobile application downloaded onto a mobile device, for example, mayallow for optional electronic tracking and simple quantification. Sensorlevels can be monitored and recorded on an optional companionapplication that allow users to keep track of their alcohol usage forlonger periods of time.

Design and characterization of a cumulative alcohol biosensor.

One embodiment may include an instantaneous electronics-free,transdermal blood alcohol content (BAC) biosensor in the form of atemporary tattoo. A wide variety of ethanol-sensing formulations may beprovided based on the particular design of the biosensor. Suchformulations may not only sense ethanol at a point in time, but alsosense and represent its accumulation over time. The design of thetemporary tattoo may therefore be configured so as to be present avisual indication system of such accumulation.

A toolkit of the temporary tattoo form factor and novel active inkformulations may be used to create a biosensor that is driven by theamount of alcohol consumed since the sensor was applied. At the core ofthe sensor is the active ink formulation. The formulation is based onthe reaction of alcohol dehydrogenase (ADH), which alongside colorchanging tetrazolium salts form the active ink. Upon ethanol reachingthe active ink containing ADH, the enzyme metabolizes ethanol toacetaldehyde and reduces NAD+ to NADH. NADH then transfers electronsthrough the electron acceptor phenazine methosulfate (PMS) to atetrazolium salt, yielding a colored product (8).

Alongside the active ink, a series of graded reference colors may beprinted. These colors may allow the users to immediately develop aqualitative sense of their cumulative alcohol consumption with theunaided eye.

FIG. 3A is a graph correlating alcohol percentages to color-strength ofan exemplary alcohol-sensing ink formulation. Using one alcohol sensingformulation, concentrations of ethanol in solution and measured colorusing both visible and spectrophotometric detection may be scanned.

FIG. 3B is a graph illustrating color change kinetics of an exemplaryalcohol-sensing ink formulation. The graph illustrates saturation within10 minutes of ethanol addition at 0.15%.

FIG. 3C is a graph correlating sweat concentrations with colorabsorbance change of an exemplary alcohol-sensing ink formulation.Specifically, the graph illustrates absorbance (color) changemeasurements with varied sweat sodium (Na+) and chloride (Cl−)concentrations, where high activity was maintained across severalalcohol concentrations.

FIG. 3D illustrates exemplary sweat samples compared to a controlsolution. Three human sweat samples collected spiked with 0.1% ethanol,showing activity is maintained relative to a control solution with 0 mMNa+.

An active ink formulation may include a tetrazolium salt such as3-(4,5-Dimethylthiazol2-yl)-2,5-Diphenyltetrazolium Bromide (MTT), aswell as commercially available ADH and PMS. The ink may be applied tothe tattoo paper via silk screening. Because the product of MTTreduction, formazan, is insoluble, its formation is an irreversiblereaction, resulting in increased color change as more ethanol isabsorbed from the sweat (9). Thus, as the user consumes more ethanol,more ethanol is excreted in the sweat over a longer period of time andcollected by the sensor, resulting in increased color intensity that canbe used as a readout of cumulative consumption. Ethanol excretion insweat is mainly independent of sweat flow rate (10), thus producing arobust cumulative metric across different conditions.

To characterize the formulations of an colorimetric reaction mixture,solution mixtures may be assayed in 24 and 48 well plates usingspectrophotometry in a Tecan M200 plate reader. Standardized 0 to 0.3%ethanol solutions may be used to confirm colorimetric readout changes byabsorbance at 540-570 nm with the use of the insoluble MTT.Reproducibility may be tested across different types of sweat bymeasuring the same 0 to 0.3% ethanol solutions in 10-100 μL solutions of0-100 mM Na+ and Cl− to mimic the known ranges in sweat concentrations(11, 12). Solutions of manually collected sweat spiked with 0 to 0.3%ethanol may subsequently be applied to the wells. Reversible ethanolsensing reactions may be characterized as presented in FIG. 3. Here, theabsorbance may be characterized at 540 nm as a measure of color changeand measured the kinetics of the color changing reaction for severalreactions (FIG. 3B). For the irreversible reaction described herein, thekinetics of ethanol sensing may be tuned such that the reaction does notsaturate. Small volumes of ethanol-spiked sweat solutions may be addedat typical sweat rates that may lead to further color change andsimulate the cumulative ethanol readout. The amount of ethanol added tothese reactions may be correlated to an estimated amount of ethanolmolecules originating from the sweat, which may be calibrated to theamount of ethanol consumed (in grams).

Having formulated the chemical reaction mixture, different patterns maybe screen printed onto paper substrates to test the kinetics of thecolorimetric reaction mixture. Screen printing may require highviscosity and thixotropy of the printed fluid, previously developed andthe use of food-grade thickeners with established safety profilesincluding xanthan gum, gum Arabic, corn starch, tapioca starch andcarboxymethylcellulose (CMC). Rigorous characterization of the screenprinting resolution properties may be done using microscopy and otherapproaches, determining that a 4% w/v carboxymethylcellulose (CMC)solution results in appropriate rheological properties with a uniformsuspension of the reaction mixture. Using this mixture as a startingpoint for the cumulative alcohol biosensor, the kinetics and colorchanges of the ethanol sensing reaction may be assayed on transfer paperusing time-lapse photography, and then analyze the color changes overtime using ImageJ (13). The same procedure may be followed as with theprevious mixtures, assaying solutions with varied ethanol and saltcontents as well as sweat with predefined ethanol content.

Data analysis and statistics: The data generated in this section mayresemble the data presented in FIGS. 3A-D. Absorbance measurements ofthe cumulative alcohol readout in the cases of water, defined saltconcentrations, and collected sweat samples may be done in triplicateand reported with standard errors when plotted. For the sensor readoutson paper, measurements may be collected using a color camera, where 3-5independent regions of interest may be analyzed for color change valuesand plotted with their variation. Measurements in this aim are expectedto be normally distributed and statistical tests and analyses may beperformed using Graphpad Prism software (14). These images andannotations may also be used to begin training the computer visionalgorithms to be developed for the mobile application.

Expected outcomes and alternatives: Developing and characterizing thecumulative alcohol-level sensor may be completed within six months.Reformulation for the cumulative ethanol readout with the irreversibledye MTT may follow a similar path, but may require adjustment of thechemical formulations and kinetics for creating the appropriate dynamicrange, including grading the reference colors. Determining such range isa key factor in determining the final active product life since itlimits the number of drinks before the wearable needs to be renewed. Alimit may be defined high enough for at least two days of heavydrinking. Also, if the kinetics of the MTT reaction are not desirable,other salts, like nitro blue tetrazolium (NBT) (15), may be used.Because it is inert, the use of CMC as a resuspension medium forscreen-printing is not expected to affect the chemical reactions in themixture, but if there are any undesired effects, other thickeners likethose listed above may be used. If screen printing produces solutionsthat are too viscous and inhibit the reaction kinetics, dilution mayoccur before screen printing, or an alternative bio-printing inkjetmethod for deposition may be used. Lastly, if the reaction with ADH doesnot function as expected, other enzymes such as alcohol oxidase (AOX),which is known to be compatible with such salts, may be used.

If it is determined that the graded reference colors are not an idealreadout system, a different gradation approach may be used. In such anapproach, the sensor may consist of multiple printed sections thatreflect a gradient of values, like an ‘energy bar” interface (FIG. 4A).These sections may be individually calibrated such that they can only beactivated once a specific cumulative ethanol content has been reached.This approach could eliminate a substantial amount of guesswork andinterpretation on the user's part, however it may require much morespecific ink formulations.

Another embodiment may include an optimized sweat collection layer thatoperates under diverse conditions, and that prevents the active ink frombeing in direct contact with the skin. Such a product may be tested incontrolled and observational studies involving a representative sampleof human subjects. Several sweat collecting—and inducing—methods (16-20)exist that are compatible with the methods described herein. More activeink colors using different salts may be used, thus enabling furthercustomization opportunities. Further embodiments may use a gradienttattoo UI when designing a biosensing temporary tattoo-like device.Thus, a user may customize their tattoo design to include (1) one morediscrete and concealed (i.e. single tattoo design element changing incolor) or (2) more explicit and potentially easier to understand (i.e.the gradient-based ‘energy bars’ approach).

Unaided-eye interpretation of color changes in sensor representing thecumulative levels of simulated transdermal alcohol concentrations over a48-hour period with 90% accuracy.

Development of computer vision algorithms to track cumulative alcohollevels.

Wearable alcohol biosensors do not require electronic devices to readcumulative alcohol concentration values, thus contributing to targetingof a wider user demographic when compared to the current state ofelectronics-dependent devices. However, some users may prefer to use asmartphone app to track cumulative values over longer periods of time.

By giving the option to these users to capture and store valueselectronically, a future application may also provide other servicessuch as trends analysis, and provide guidance or coaching

Recognizing tattoos and interpreting them is an active area of research(21, 22, 23, 24), faced with challenges that include their arbitrarydesign, and arbitrary placement—and deformation—when applied ondifferent skin surfaces. An important part of the existing researchfocuses on features outside of the scope of alcohol biosensing (e.g. incriminology). A computer vision pipeline may be provided that istailored to reading biomarker values and that tracks cumulativeconcentration values from a semi-arbitrarily designed temporarytattoo-like cumulative alcohol biosensor that can be placed on differentparts of the body. Such a pipeline is composed of five modules: capture,detection, identification, interpretation, and storage.

The first module (FIG. 4A) may rely on a conventional smartphone'scamera to take a raw image of the biosensor placed on the skin. Thesecond module (FIG. 4B) uses the raw image as an input to detect thebiosensor—a 2D surface—on a skin area of the body—a 3D model. Because animportant differentiator of a wearable alcohol biosensor is that it canbe easily customized to have a range of shapes placed on a skin surface,detection may use a convolutional neural network (CNN) for image patchlabeling. In such an embodiment, a sliding window is used to classifyeach region traversed as either belonging or not to a tattoo. The moduleoutput is a masked image region and the specific deep learningarchitecture to achieve this assumes a model similar to AlexNet (26).

Training of the CNN may happen initially on temporary tattoos printedwith regular inks. Training may always include a representative sampleof skin types along the Fitzpatrick phototyping scale. A third module(FIG. 4C) performs feature extraction from the masked image by extendinga version of Fast Retina Keypoint (FREAK) (27). The modification isbased on work originally described to detect logos from documents (28,29) using a version of the scale invariant feature transform (SIFT)(30). FREAK key descriptors generally perform faster on embedded systemssuch as smartphones. Some approaches may be based on detection of logossince in the beginning the biosensors may be composed of simple strokesand filled areas. Further refinements or other methods altogether may beused later for more sophisticated designs. Regarding future usercustomization of the design of a tattoo, the masked region ofinterest—the input to this module—may be matched against a referenceshape in a dataset, since customized tattoos may be initially designedor uploaded through a mobile app. The output of this module is theextracted shape and its associated reference shape. The next module(FIG. 4D) interprets the differences between the extracted and referenceshapes to assess the cumulative alcohol concentration values. As part ofthis process the extracted shape goes through a color normalizationmethod (31) to eliminate the effects of illumination, preserving theinherent colors of the sensor and reference colors, and only allowingcolor variations related to the cumulative alcohol concentrations. Thismethod assumes the illumination to be reasonably well modelled asblackbody radiation (32). Also, the extracted shape is treated as adeformation of the reference shape. It is defined mathematically bymapping from the reference shape x to the deformed shape y by atransformation function (33).

At this point, the reference shape may be populated with normalizedcolor values from the extracted shape across its surface area. To assessthe cumulative alcohol concentration levels, calibration may be done byrunning a more granular sliding window of n×n pixel size to traverse thecolor-populated reference shape. In each new region, color value may bematched against the color versus concentration curves calibrated asdiscussed above. Additionally, the color curves may be color-normalizedbefore use. Finally, the last module (FIG. 4E) stores all the datacollected including the extracted shape but excluding actualphotographic images in remote servers, thus helping preserve userprivacy and the potential upload of non-sensor images.

Expected outcomes and alternatives: The various aspects described hereinthat can be applied to a range of sensors sharing the temporarytattoo-like form factor, including the cumulative alcohol monitoringbiosensor described herein, or the previously developed instantaneousalcohol monitoring sensor. Modules may be added or improved while alsotraining and calibrating the pipeline for the specific cumulativealcohol sensing application described herein. Highly qualitative data ofcumulative alcohol values may be collected and used for training andcalibrating until there is a more robust and semi-quantitative solutionin place, which may be specific to a user. Reference colors may be usedon the temporary tattoo, using the color versus concentration curvesrecorded as discussed above, thus allowing for an increase in accuracy.As described herein, calibrating the pipeline may allow for capture of agradient tattoo UI (i.e. the ‘energy bars’ approach), where assessmentof biosensor values may be easier. Also, because different smartphonemodels have different native RGB color spaces, color transformationtechniques may be applied to a common color space using the full cameraprofile when available, or by using a standard color matrix.

Convolutional Neural Network (CNN) described for the detection modulemay be trained, thereby further increasing its robustness to detect atemporary tattoo at a wider range of camera angles, lighting conditions,skin types, and parts of the body. Other aspects of the pipeline may beenhanced including local storage, which may happen under a commercialsetting integrating with services provided by third party companies orplatforms such as Apple HealthKit (34). In general, the companionapplication may be robust enough to be ready to be used by consumers,initially during controlled and observational studies, and later in acommercial setting. Being user privacy protection a high concern for anyconsumer-oriented alcohol monitoring application, in addition to the useof standard user data encryption methods, commercially availableservices that involve Differential Privacy (35) may be integrated insystems described herein, where the information stored in remote serversis randomly distorted in known statistical quantities, thus preventinganybody from pinpointing specific user data to an individual.

Computer vision interpretation of data color changes in sensorrepresenting the cumulative levels of simulated transdermal alcoholconcentrations over a 48-hour period with 90% accuracy.

FIG. 5 illustrates a variety of customized designs for wearable alcoholbiosensors. Such designs may include a single active ink used on asingle design element. Further designs may include multiple active inksused on multiple design elements, each becoming visible at differentcumulative alcohol concentration levels, forming a gradient ofcumulative values.

The detailed description of the technology herein has been presented forpurposes of illustration and description. It is not intended to beexhaustive or to limit the technology to the precise form disclosed.Many modifications and variations are possible in light of the aboveteaching. The described embodiments were chosen in order to best explainthe principles of the technology and its practical application tothereby enable others skilled in the art to best utilize the technologyin various embodiments and with various modifications as are suited tothe particular use contemplated. It is intended that the scope of thetechnology be defined by the claim.

What is claimed:
 1. A wearable device for detecting cumulative alcoholconsumption, the wearable device comprising: an adhesive layer thatadheres to skin and that allows sweat from the skin to pass through; anda customizable ink layer that reacts irreversibly to change color alonga gradient as ethanol is detected in the sweat, wherein the customizableink continues to increase color intensity along the gradient as ethanolcontinues to be detected in the sweat over time.
 2. A method fordetecting cumulative alcohol consumption, the method comprising:receiving input indicative of a reaction of a wearable biosensor at apoint in time, wherein the reaction occurs in response to detection ofethanol consumption; executing instructions stored in memory, whereinexecution of the instructions by a processor identifies that thereceived input is indicative of a cumulative amount of ethanolconsumption; and stores the cumulative amount of ethanol consumption inmemory, wherein the cumulative amount of ethanol consumption is storedin association with the point in time.
 3. The method of claim 2, whereinreceiving the input comprises receiving an image of the wearablebiosensor, and wherein the image is captured by a camera after thewearable biosensor visibly indicates the reaction.
 4. The method ofclaim 2, wherein identifying that the received input is indicative of acumulative amount of ethanol consumption comprises classifying aplurality of regions of the image as belonging to the wearable biosensorand not belonging to the wearable biosensor.
 5. The method of claim 4,wherein the classification is based on a sliding window of aconvolutional neural network for image patch labeling.
 6. The method ofclaim 4, wherein classifying the plurality of regions comprisesextracting one or more masked image regions.
 7. The method of claim 4,wherein classifying the plurality of regions includes matching at leastone region to one or more reference shapes stored in a database memory.8. The method of claim 4, further comprising normalizing the image forcolor to eliminate effects of illumination.
 9. The method of claim 4,wherein classifying the plurality of regions comprises: detecting acolor value of at least one region; and matching the detected colorvalue to a stored chart of calibrated color concentration values.